Plasma kinetic effects on interfacial mix and burn rates in multispatial dimensions

• Published in: Physics of plasmas 2019-06, Vol.26 (6)
• Main Authors: Yin, L., Albright, B. J., Vold, E. L., Nystrom, W. D., Bird, R. F., Bowers, K. J.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Computer simulation; Flux density; Gravitational constant; Inertial confinement fusion; Marble; MATHEMATICS AND COMPUTING; Particle in cell technique; Perturbation; Plasma physics; Plasmas (physics); Scaling; Taylor instability; Three dimensional models; Two dimensional models; Wavelengths
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.5109257

The physics of mixing in plasmas is of fundamental importance to inertial confinement fusion and high energy density laboratory experiments. Two- and three-dimensional (2D and 3D) particle-in-cell simulations with a binary collision model are used to explore kinetic effects arising during the mixing of plasma media. The applicability of the one-dimensional (1D) ambipolarity condition is evaluated in 2D and 3D simulations of a plasma interface with a sinusoidal perturbation. The 1D ambipolarity condition is found to remain valid in 2D and 3D, as electrons and ions flow together required for J = 0. Simulations of perturbed interfaces show that diffusion-induced total pressure imbalance and hydroflows flatten fine interface structures and drive rapid atomic mix. The atomic mix rate from a structured interface is faster than the ∼ t scaling obtained from 1D theory in the small-Knudsen-number limit. Plasma kinetic effects inhibit the growth of the Rayleigh-Taylor instability at small wavelengths and result in a nonmonotonic growth rate scaling with wavenumber k with a maximum at a low k value, much different from Agk (where A is the Atwood number and g is the gravitational constant) as expected in the absence of plasma kinetic effects. Simulations under plasma conditions relevant to MARBLE separated-reactant experiments on Omega and the NIF show kinetic modification of DT fusion reaction rates. With non-Maxwellian distributions and relative drifts between D and T ions, DT reactivity is higher than that inferred from rates using stationary Maxwellian distributions. Reactivity is also found to be reduced in the presence of finite-Knudsen-layer losses.